In any microcontroller the Boot-Loader is the first code which executes before the application code does. The major function of the Boot-Loader is to load the application code into the flash memory of the microcontroller and execute it. In AVR microcontroller the Self Programming Mode (SPM) helps the Boot-Loader to load a particular application from where the application binary is stored.The Boot-Loader may receive the code binary from other memory chips, SD-cards or through the serial port of the microcontroller in case of serial programming. It is then with the help of the SPM that the microcontroller write the binary code into the application flash section. In this particular project the operation of a Boot-Loader code using the SPM is demonstrated by re-writing flash memory with the code binary which has already been flashed into the built-in EEPROM of the ATMEGA16. The hardware used in this project includes ATMEGA16 as microcontroller, USBASP as the programmer and the software used are AVR STUDIO4 as IDE and AVR-BURNO-MAT as the burner software. 

The Self Programming Mode (SPM) is a feature which enables a microcontroller to program its own flash memory. Using the SPM a microcontroller can program itself with an SPM code. The SPM is commonly used with the microcontroller Boot-Loader codes which help to program the microcontroller serially. In AVR microcontroller the SPM is available only for the code running in the BLS of the flash memory. With the help of the SPM a code in BLS can rewrite the application flash memory entirely or a part of it. It can even rewrite its own code in the BLS section. The SPM is a key factor of the Boot-Loader code since the major function of the Boot-Loader is to load an application code into the application flash section. The Boot-Loader may receive the code binary from other memory chips, SD-cards or through the serial port of the microcontroller in case of serial programming.